The present invention relates to a cleaning unit incorporated in a copier, printer, facsimile apparatus or similar image forming apparatus for removing a toner deposited from a photoconductive element.
It is a common practice with a copier, for example, to electrostatically form a latent image on a photoconductive drum and cause a toner to deposite on the latent image to produce a toner image matching a document image. After the toner image has been transferred to a recording medium, e.g., paper sheet, part of the toner usually remains on the photoconductive drum and has to be removed before the next copying cycle begins. A cleaning device for removing the toner remaining on the drum may be implemented by a fur brush, as well known in the art. In this type of cleaning device, the fur brush is made of a conductive material and held in pressing contact with the photoconductive element to scrape off the toner remaining on the drum. The toner deposited on the fur brush is electrostatically transferred to a collecting roller, and then a collecting blade removes the toner from the collecting roller. The removed toner is conveyed to the outside of the cleaning device by a coil. The fur brush is provided with some elasticity since it has to rotate while thrusting into the drum and the collecting roller to a predetermined extent. However, when left stationary over a long period of time, the fur of the fur brush remains in the collapsed position and cannot return to the original position. In such a condition, the cleaning device fails to fully remove the toner or to collect it in an expected manner, resulting in the degradation of image quality. In light of this, the fur brush may be spaced apart from the drum or from the collecting roller while an image forming operation is not under way, as proposed in the past. With such a conventional implementation, however, it is impossible to completely free the fur brush from collapse since the fur brush remains in pressing contact with one of the drum and collecting roller, although it may be spaced apart from the other.